Question 363839
.72x+.80(840-x)=.75*840
.72x+672-.80x=630
-.08x=630-672
-.08x=42
x=42/.08
x=525 are boys.
525/840=5/8 are boys.
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840-525=315 are girls.
Proof:
.72*525+.80*315=.75*840
378+252=630
630=630